Antigen binding molecules, including antibodies, and fragments such as Fabs, F(ab′)2, scFvs, etc, are used in immunotherapy and solid phase-based applications such as biosensors, affinity chromatography, and immunoassays. These antibodies and other antigen binding molecules gain their utility by virtue of their ability to specifically bind their targets.
Anti-idiotypic antibodies are a subset of antibodies, and are antibodies raised against immunizing antibodies. These anti-idiotypic antibodies demonstrated specific binding against the idiotopes (unique antigenic determinants on the surface of the antibodies) of the immunizing antibodies. Anti-idiotypic antibodies can be generally classified into three distinct groups: (1) antibodies are those that recognize idiotopes distinct from the antigen-binding site (ABS) on immunizing antibodies; (2) antibodies that recognize epitopes within the ABS and mimic the structure, and forming the so-called “internal image,” of the nominal antigen; and (3) antibodies that recognize epitopes within the ABS without the structural resemblance of the nominal antigen (see, e.g., Pan et al., (1995) FASEB J 9:43-49).
FMC63 is an IgG2a mouse monoclonal antibody that recognizes CD19, which is expressed on the surface of B cells (Zola et al., (1991) Immunol Cell Biol 69:411-22). Single chain variable fragments (scFv) formed from FMC63 comprise the targeting component of some chimeric antigen receptors (CARs) (Kochenderfer et al., (2009) J Immunother 32(7):689-702), and the scFv of FMC63 has previously been used to generate anti-FMC63 antibodies (Jena et al., (2013) PLoS ONE 8(3):e57838).
Disclosed herein are rabbit antigen binding molecules, including antibodies, that specifically bind to the anti-CD19 scFv FMC63 (SEQ ID NO: 1), as well as molecules comprising these sequences and cells presenting such molecules. Humanized forms of the disclosed rabbit antigen binding molecules also form as aspect of the disclosure. Applications and uses of these antigen binding molecules are also disclosed.